Coal is an organic sedimentary rock which is the prehistoric vegetation that are deposited at swamps, subjected to heat and pressure over million of years. This is composed mainly of carbon, hydrogen and oxygen. Coal along with oil and gas is fossil fuel, can also be called combustible rock.
Formation of coal
Coal is formed by the deposition of plant debris in a swampy area where conditions are favourable for the generation of coal. Condition to form coal are area where water does not dry up, plant debris are continuously being submerged in the water that no decay process can be carried out. The plant debris accumulates slowly at a place which further generate into coal seam. For a few feet fifty or hundred feet area of coal seam, it takes a very long time about thousands of years at which the water level should remain constant so that no decay process can be stimulated or else seam generation won't be carried out.
Coal formation started in the Carboniferous period, which is spanned as 360 to 290 million years ago is known as first coal age. Due to tectonic movements, silt and other sediments build together with the swamp and peat log areas buried at great depths. With burial of the plant remains to depths which are great enough with temperature and pressure, turned the plant debris into peat and then into coal.
Energy of coalThe energy we get from the coal is the solar energy stored by the plants during their life time by a process we will be well aware of, the photosynthesis. This stored energy remains in the body of a plant which in turn is submerged in the water of a swamp. If this plant is not preserved in the water to form coal, the energy stored will be released by the decay process.
Types of coal
Coal quality depends upon the following factors
- Vegetation variation from which it is formed
- Depths of burial
- Temperature and pressure at those depths
- Length of time taken by the coal deposits
Over many more million years of temperature and pressure continuous effect, lignite faces further changes with progressively organic maturity transforming it into sub-bituminous coals.
Further cooking under favourable continuous temperature and pressure, organic matter matures more and more forming bituminous and at last the high grade anthracite. These are hard coal with more blackish colour.
Uses of coals
Coal has a wide range of uses, it can be used for different purposes. The most significant use of coal is generation of electricity in power plants. Electricity is generated by burning of coal in power plant which is also called as thermal coal. Another use of coal is in metallurgical industry, making of steel which is know as metallurgical coal. Coal also have domestic use which can be for heating purpose by coal fire or can be used for cooking, mostly barbecue.